Computer simulation is a conventional tool for designing a new system. System simulation has been used for such purposes as improving systems, reducing risk, and reducing system design costs. Fluid systems, power systems, and communication systems are but a few examples of the many types of systems that have been modeled.
There are a variety of systems and a variety of models. Conventional design of a model is solely concerned with the successful running of a system under a certain set of conditions. Many good software packages are commercially available to simulate specific systems in this manner. Different systems lend themselves to different types of models. Among the types of models that are conventionally used to simulate systems are rule-based models, physics-based models, and hardware-in-the-loop models. Nevertheless, if a system designer wishes to ascertain how a system will respond to a system-degrading event, conventional modeling may not suffice.
A system can be dependent on another system. As an example, simulation of systems prone to damaging events may require modeling of such events as fire spread, smoke spread, and flooding. A simulative strategy involving the separate simulation of each of these different systems erroneously assumes that each system is ideal. For instance, if a pump in a fluid system relies on the power provided by a power system, then there may be conditions (e.g., power failure) that are not accounted for when simulating the fluid system alone. Furthermore, system-impactive events that occur in-between systems may not be accounted for when simulating systems individually. These kinds of interdependencies between systems suggest the need for simulation of a “system of systems.”
The consideration of interactions between interdependent systems is important to understanding how failures in one system propagate into other systems, and how these failures affect the operation of the system of systems. In conventional simulation involving design of a single system that is a member of a system of systems, the interdependence between the systems is not considered beyond the interfaces between the systems. A system's “recoverability”—i.e., the ability to restore the system to a working state after an interruption—often represents a critical aspect of system design. For purposes of performing recoverability analysis of a system, conventional simulative approaches may not be truly indicative of real-world consequences.
It is considerably more challenging to simulate a system that is composed of multiple systems than it is to simulate a single system. The need exists for a methodology for simulating a system of interdependent systems so as to accurately and insightfully account for interdependencies between the systems.